1. Field of the Invention
The present invention relates to a data recording/reproduction device for recording and reproducing data of all types such as computer data and relates in particular to random access type data recording/reproduction devices. More specifically, the present invention relates to disk type data recording/reproduction devices utilized while mounted in a host device such as a computer system and relates in particular to disk type data recording/reproduction devices for recording and reproducing for recording and reproducing computer data requiring reliability, and video data and audio data requiring real-time characteristics.
2. Description of the Related Art
All types of information processing systems such as general-purpose computers contain a data recording/reproduction device to store large quantities of data and data for large scale applications in a non-volatile manner. Data recording/reproduction devices are for example comprised of disk type devices to store data on a rotating disk and tape type devices to store data on wound reel of tape.
A typical disk device is the HDD or hard disk drive. The hard disk drive has an amazing data storage capacity due to advances made in magnetic head technology and signal processing technology, etc. From 1990 up to the present for example, the surface recording density of data has increased approximately 60 percent each year. One 3.5 inch disk is expected to be capable of recording 10 to 20 gigabytes of data some time after the year 2000. In other words, one hard disk drive unit having a plurality of disks would have a recording capacity in excess of 100 gigabytes.
Therefore, by utilizing high efficiency digital moving picture compression technology such as DV (digital video) or MPEG2 (Moving Picture Experts Group Phase 2) made practical in recent years, moving picture information for a plurality of channels can be recorded on and reproduced from a hard disk drive, and multichannel video recorders capable of using a hard disk drive as a recording medium are now feasible.
However, from a historical point of view the hard disk drive was developed as an external storage device for computers and technical progress has been made in improving so-called discrete text type data and in making random access of data as fast as possible. In other words, hard disk drive operation is broken up or discrete along the time axis.
The computer system (hereafter “host”) incorporating the hard disk drive (HDD) issues commands (hereafter “host commands”) specifying the recording or reproduction of data. The operations in response to each command from the host are executed one at a time as discrete operations. Restated, the hard disk drive guarantees high reliability but does not guarantee the recording or reproduction operation will finish within a specified time (real time guarantee).
One cause that prevents guaranteeing the actual time required for an operation is the retry process. The recording and reproduction of data on a hard disk drive is performed in short data sector unit (for example 512 bytes each) equivalent to the (information) packet used in communications technology. In the retry process, an operation is repeated again when an error occurs in implementing instructions such as to perform recording or reproduction of a data sector assigned by the host.
Various types of errors cause the retry operation to be used. On such error is in the operation (seek) to move the head to the target sector. To resolve the seek error, the recording and reproducing onto that target sector must be abandoned and continued elsewhere or retry operation must be performed. One retry requires from a few to several dozen milliseconds of wasted time and is a factor in poor real-time characteristics. Next, is retries (Write-Retry) during recording of data. If a deviation in the head position exceeding the established tolerance occurs such as from mechanical shock applied for example externally onto the hard disk drive during recording onto one data sector, then the recording operation will be halted. After waiting for the head to be restored to a normal position and the head to once again come to a position directly above the applicable sector by disk rotation, the recording of data onto the applicable sector starts once again (Write-Retry).
A third cause is retries (Read-Retry) during data reproduction (or playback). When an error is determined to occur that exceeds the correction capacity of the ECC (error correction code) in each sector during reproduction of one data sector, the operation stands by until the head once again comes to a position directly above the applicable sector by disk rotation and reproduction of the applicable sector starts again (Read-Retry). Further, when determined that the error was not corrected by one Read-Retry, a second Read-Retry is implemented. If the error is not a soft error due for example to noise, but is a hard error due definite cause such as damage of the magnetic film on the disk, then Read-Retry might be attempted 10 times or more without correctly reading the data, thus requiring at least 100 milliseconds of wasted time. Retries can therefore be a fatal problem in guaranteeing the actual time for a recording/reproduction operation.
The maximum number of retries implemented and other such error processing methods are fixedly incorporated into the design of related hard disk drives so that effective control according to the overall status of the disk recorder was not possible. Also, in the related art, a means was proposed for implementing or prohibiting retries without restrictions (For example, in a portion of the interfaces standards, of the ATA (AT-Attachment) established by ANSI (American National Standards Institute)) however a means for setting a maximum allowable time required for error processing, or a means for dynamic control according to the urgency or criticality (namely, the real-time characteristics) of recording and reproduction were not proposed.
In the disk type data recording/reproducing device of the related art, it was also assumed that data files would be handled discretely from each other so that instructions for recording or reproducing on individual sectors were treated as mutually unrelated items. So in applications such as multi-channel video and recorders with hard disk drives, even when recording/reproducing with a small number of long AV data streams, information on what data stream that the data for a recording/reproducing instruction belonged to was not utilized.
Therefore as related above, in the related art, the host device incorporating the disk type data recording/reproducing device had no simple means for monitoring items such as the error processing time of the disk device. Consequently, the related art had the problem that the continuous real time required during the recording or reproducing of information such as moving picture or audio information could not be guaranteed.
Still further, in the disk type data recording/reproducing device of the related art, the individual recording/reproducing operations were implemented without assigning a mutual rank or order (relation) so that a high throughput could not always be maintained.